Dynamic mechanical analysis (DMA) and low temperature impact properties of metallocene polyethylenes

As a result of the very high co-monomer content and homogeneous short branch distributions made possible by the metallocene catalyst, superior low temperature mechanical properties are possible. We have studied a series of these polymers varying in density from 0.87 to 0.92 kg l(-1) using dynamic mechanical analysis. Compared with conventional polyethylenes, the beta relaxation was shifted to as low as -44 degrees C. Concurrently, low temperature impact properties were evaluated from about -100 degrees C to ambient. The impact response with temperature was in good agreement with the calculated response based on loss modulus.